Exhaust device for rotary piston engine



June 10, 1969 TAKAHARU KOBAYAKAWA 3,443,727

EXHAUST DEVICE FOR ROTARY PISTON ENGINE Sheet 1 of 2 Filed March 14, 1968 vFIG! FIG.2

June 10, 1969 TAKAHARUKOBAYAKAWA 3,448,727

EXHAUST DEVICE FOR ROTARY PISTON ENGINE Filed March 14, 1968 Sheet 2 of 2 SOUND PRESSURE (db) FREQUENCY (cps) United States Patent US. Cl. 123-8 3 Claims ABSTRACT OF THE DISCLOSURE This invention provides an improved exhaust device for rotary piston engine to reduce the occurrence of the exhaust noise when the working fluid is exhausted, and the improvement resides in that a plurality of exhaust ports divided by partitions are provided on the center housing of the casing, the exhaust ports being successively opened as the rotor rotates.

This invention relates to an improved exhaust device for rotary piston engines.

Generally, with a rotary piston engine in which each process, such as intake, compression and explosion of the working fluid and exhaust, is performed by the planetary rotating motion of a polygonal rotor in a casing which comprises two parallel side housings and a center housing having a polyarciform inner face interposed between them, there are two ways in exhausting the working fluid.

According to the first Way, which is known as a peripheral exhaust type, a single exhaust port is provided on the center housing, through which port the Working fluid is exhausted, while according to the second Way, which is known as a side exhaust type, a single exhaust port is provided on the side housing, through which port the working fluid is exhausted. Each of the aforesaid two ways has its merits and defects, however, in view of the basic structure of this type of engine, the first Way, i.e. the peripheral exhaust type is known to be superior to the second way, i.e. the side exhaust type, in regard to exhaust efliciency which effects the output efficiency of the engine, as the working fluid is rapidly exhausted through the exhaust port, because the passage resistance is small and it is possible to make a sudden change in the opening area of the exhaust port from the beginning of the opening to its complete opening.

In the past, a single port with the necessary area of opening had been adopted as the exhaust port on the center housing. This is excellent in exhaust efficiency, as mentioned above, but, at the same time, as the opening ratio of the exhaust port increases sharply with the rotation of the rotor and the expansion ratio of the working fluid in the working chamber becomes large simultaneously with the opening of the exhaust port, a turbulent flow occurs in the vicinity of the exhaust port, which results in making it impossible to prevent an unpleasant exhaust noise, e.g. from the order of to 10 c.p.s., and especially high frequency noise from occurring.

An object of the present invention is to provide an improved exhaust device of the peripheral exhaust type for the rotary piston engines having a superior exhaust efficiency and a high output power.

Another object of the present invention is to provide an improved exhaust device to reduce the occurrence of an unpleasant exhaust noise of especially high frequency.

In accordance with the present invention, the exhaust port on the center housing consists of a plurality of ports, each having a comparatively small opening area so as to prevent the occurrence of the turbulent flow caused by 'ice the abrupt increase of opening rate of the exhaust port as the rotor rotates and by the sudden expansion of the working fluid accompanying the opening of the exhaust port and especially, to prevent the occurrence of high frequencyexhaust noise caused thereby.

The present invention will be described more in detail referring to illustrative embodiments shown'in the drawing, in which:

FIG. 1 shows vertical section front view of a rotary piston engine equipped with an embodiment of the exhaust device in accordance with the present invention;

FIG. 2 is a partial side view of the device of- FIG. 1 illustrating the exhaust ports;

FIG. 3 shows another embodiment of the exhaust device of the present invention; and

FIG. 4 shows a graph in which a comparison is made on the sound pressure of the exhaust noise versus frequency between the rotary engine equipped with the exhaust device according to the present invention and the conventional rotary engine.

In FIGS. 1 and 2, 1 is a center housing with a polyarciform inner face; 2 and 2, side housings fitted on both sides of center housing 1; 3, the polygonal rotor that is supported by eccentric shaft 4 and makes a planetary rotation inside the casing consisting of the center housing 1 and the side housings 2, 2; 5 is an intake port provided on the center housing 1; 6a, 6b and 6c are the exhaust ports which are provided on the center housing, separated by partitions 7a and 7b, respectively, and designed so that these exhaust ports successively communicate with working chamber 8 accompanied with the rotation of rotor 3.

In such a structure, the opening rate of the exhaust ports shows a comparatively gradual increase with the rotation of rotor 3 and, at the same time, exhaust port 6a, which is separated from port 6b by partition 711, has a comparatively small opening area when it is opened and the working fluid in working chamber 8 is exhausted. Therefore, the working fluid does not expand suddenly in the port 6a, and when the rotor 3 further rotates, exhaust ports 6b and 60 will open successively in this order and the Working fluid pressure will decrease gradually, so that it is possible to prevent a high frequency exhaust noise from occurring.

Another embodiment shown in FIG. 3 is similar to the foregoing embodiment shown in FIG. 2, and as the rotor 3 rotates, exhaust ports 6a, 6b and 60, which are separated by partitions 7a and 7b, open in this order and, in consequence, the working fluid pressure in the working chamber decreases gradually. However, in this embodiment, the opening rate of the exhaust ports is changed by designing the exhaust ports such that, after exhaust port 6a begins to open and opens to some extent, exhaust port 6b begins to open, and before exhaust port 6!) is fully opened, exhaust port 60 begins to open.

As the present invention was designed in the structure mentioned above, the opening rate of the exhaust port is comparatively gradual and there is no danger of turbulent flow occurring in the vicinity of the exhaust ports caused by a sudden expansion of the working fluid, in spite of the fact that the exhaust ports are provided on the center housing. Therefore, the occurrence of an unpleasant exhaust noise, particularly of a high frequency, can be prevented.

FIG. 4 shows sound pressure on ordinate in db and noise frequency on abscissa in c.p.s. The Curve B shows exhaust noise sound pressure taken on the conventional rotary piston engine equipped with a single exhaust port on the center housing, while the Curve C shows that taken on the rotary piston engine equipped with the exhaust device of the present invention. As apparent from the graph, the Curve C shows that the noise sound pressure is significantly decreased in comparing to the Curve B especially in high frequency nozzle range.

What is claimed is:

1. In a rotary piston engine comprising a casingcom prising two parallelly arranged side housings and a center housing mounted therebetween, and a rotor supported by an eccentric shaft so as to planetarily rotate within the casing to perform the steps of intake, compression, explosion and exhaust of a working fluid, an exhaust device having a plurality of exhaust ports provided on the center housing with partitions separating these ports from each other, the exhaust ports being successively opened as the rotor rotates.

2. The exhaust device according to claim 1, in which a 3; The exhaust device according to claim 1, in which a succeeding port will begin to open after a preceding port is opened to some extent.

References Cited UNITED STATES PATENTS 0 CARLTON R. CROYLE, Primary Examiner.

-D. HART, Assistant Examiner.

US. Cl. X.R.

succeeding port will open just after a preceding port is 15 91-56 fully opened. 

